1. Field of the Invention
The present invention relates to an engine cooling system for an all-terrain vehicle provided with a water-cooled engine.
2. Description of the Related Art
Referring to FIG. 8, a conventional engine cooling system for an all-terrain vehicle provided with a water-cooled engine includes a radiator 101, a cooling fan 102 disposed behind the radiator 101, and a water reserve tank, not shown. The radiator 101 is covered with the front fender of the vehicle. A water filler port 106 is formed in the upper wall of the radiator 101 and is closed by a radiator cap 109 detachably attached to the radiator 101. A water inlet 110 is formed in one upper corner of the rear surface of the radiator 101 at a level at a predetermined distance below the upper end of the radiator 101. A water outlet 111 is formed in one lower corner of the rear surface of the radiator 101. The water inlet 110 is connected to an outlet 113 of the water jacket of the engine by a return pipe 112. The water outlet 111 is connected to a water pump 103 by a water supply pipe 116. A thermostat, not shown, is placed in a cooling water outlet formed in the cylinder head of the engine. Prior art relating with the present invention is disclosed in JP-U No. Hei 5-10743.
When the radiator 101 provided with the water filler port 106 formed in the upper wall thereof as shown in FIG. 8 is mounted on an all-terrain vehicle as shown in FIG. 1, the water filler port 106 is located near a position indicated by the arrow A in FIG. 1, i.e., a position near the lower surface of the front fender 12. Therefore, when supplying water into the radiator 101, the operator needs to reach out a hand through a gap between the lower surface of the front fender 12 and the upper end of a side panel 120 to remove the radiator cap 109, which requires difficult work for supplying water into the radiator 101.
The radiator 101 of the engine cooling system shown in FIG. 8 is provided with the water filler port 106 in its upper wall to place the water filler port 106 at a desired level. However, only a limited space is available in the body of the vehicle for placing the radiator 101 and there are restrictions on the level of the radiator 101. Consequently, the water filler port 106 cannot be located at a high level enough to secure a sufficient pressure head difference between the outlet 113 of the water jacket of the engine and the water filler port 106. Thus, air remaining in the radiator 101, the water jacket and the piping cannot be easily removed when supplying water into the radiator 101, water must be supplied at a low rate and the work for supplying water into the radiator 101 takes much time.
Since the water inlet 110 of the radiator 101 is formed at a level at a predetermined distance below the upper end of the radiator 101, air is not easy to escape from the radiator 101 when water is supplied into the radiator 101.
Accordingly, it is an object of the present invention to provide an engine cooling system for an all-terrain vehicle, including a radiator provided with a radiator cap which can be easily put on and removed from the radiator and capable of being supplied with water by simple, efficient work, and capable of making difficult the accumulation of air in cooling water circulating passages.
According to the present invention, an engine cooling system for an all-terrain vehicle provided with a front fender, a steering handlebar and an engine provided with a water jacket and mounted on a body frame at a position between front and rear wheels comprises a radiator provided with a water inlet and disposed in a front part of the body frame, a water filling cup provided with a water filling opening covered with a cap, said water filling cup being formed as a different body from the radiator and a thermostat case holding a thermostat therein; wherein the water filling cup and the thermostat case are placed in a part of a connecting pipe connecting the water inlet of the radiator and an outlet of the water jacket, at the highest level in a cooling water circulating passage and located in a space under the front fender and near the steering handlebar.
In the engine cooling system thus configured, the position of the water filling cup is not subject to restrictions placed by the disposition of the radiator and the water filling cup can be disposed in a proper space in the body frame, such as a space near the steering handlebar for the efficient use of the space in the body frame. A large pressure head difference can be secured between the water filling opening of the water filling cup and the outlet of the water jacket of the engine, air remaining in the cooling water passage can be smoothly removed, water supplying work can be efficiently achieved, and air will not accumulate in the water jacket of the engine.
Preferably, a protruded portion may be formed on the front fender so as to surround a steering shaft connected to the steering handlebar, the water filling cup and the thermostat case may be placed inside the protruded portion, and the protruded portion may be provided with an access opening for the water filling cap.
Thus the water filling opening and the thermostat can be easily disposed at a high level, and the cap of the water filling cup can be easily removed by reaching out a hand through the access opening to the cap, and water can be easily supplied through the water filling opening of the water filling cup into the radiator.
Preferably, the water inlet of the radiator may be formed in the upper wall of the radiator.
Thus the connecting pipe connecting the water inlet of the radiator and the outlet of the water jacket of the engine can be easily arranged and air can be easily removed from the cooling water passage.